We are investigating the behavioral effects of early protein malnutrition in rhesus monkeys. Behaviors under study include discrimination learning, social behavior, exploratory behavior, general activity, locomotor development, and food preferences. Effects of postnatal protein deficiency are being examined as well as effects of protein malnutrition of the mother during gestation. Studies are in progress to determine whether effects of early malnutrition persist after nutritional rehabilitation at different ages. We have attempted to correlate behavioral changes with changes in the growth and biochemical development of the brain. BIBLIOGRAPHIC REFERENCE: Neuringer, A. and Neuringer, M. Learning by following a food source. Science 184: 1005-1008, 1974.